*Review* **Gastrointestinal Microbiota and Type 1 Diabetes Mellitus: The State of Art**

#### **Marilena Durazzo \*, Arianna Ferro and Gabriella Gruden**

Department of Medical Sciences, University of Turin, C.so A.M. Dogliotti 14, 10126 Turin, Italy; arianna.ferro@unito.it (A.F.); gabriella.gruden@unito.it (G.G.)

**\*** Correspondence: marilena.durazzo@unito.it; Tel.: +39-0110918473

Received: 14 October 2019; Accepted: 29 October 2019; Published: 2 November 2019

**Abstract:** The incidence of autoimmune type 1 diabetes (T1DM) is increasing worldwide and disease onset tends to occur at a younger age. Unfortunately, clinical trials aiming to detect predictive factors of disease, in individuals with a high risk of T1DM, reported negative results. Hence, actually there are no tools or strategies to prevent T1DM onset. The importance of the gu<sup>t</sup> microbiome in autoimmune diseases is increasingly recognized and recent data sugges<sup>t</sup> that intestinal dysbiosis has a pathogenic role in T1DM by affecting both intestinal immunostasis and the permeability of the gu<sup>t</sup> barrier. An improved understanding of the mechanisms whereby dysbiosis in the gu<sup>t</sup> favors T1DM development may help develop new intervention strategies to reduce both the incidence and burden of T1DM. This review summarizes available data on the associations between gu<sup>t</sup> microbiota and T1DM in both experimental animals and humans and discusses future perspectives in this novel and exciting area of research.

**Keywords:** type 1 diabetes; microbiota; microbiome; auto-immunity; gu<sup>t</sup> permeability
